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According to a recent news release, the FEI Company (listed on the NASDAQ stock exchange under the symbol FEIC) has developed a new fully automatic gunshot residue (GSR) package. FEI Company develops, produces and markets instruments for sub-micrometer-level imaging, analysis, modification and fabrication. Its product portfolio includes focused ion beam (FIB) workstations, transmission electron microscopes (TEM), scanning electron microscopes (SEM), and systems using these technologies in combination. The company markets these instruments under the FEI and Philips brand names to semiconductor and data storage device industries, universities and research institutes as well as to organizations involved in materials research and life sciences.

While FEI Company is headquartered in Eindhoven, The Netherlands, it also has three other development and production centers, in Hillsboro, Ore., Boston, Mass., and Brno, Czeck Republic. Philips Electronics holds 55% of the FEIC shares. It employs more than a thousand employees in these centers and in its sales offices scattered around the world. Its active Website can be found at http://www.feic.com

According to the company's news release, the Gunshot Residue Package from FEI Company eliminates the tedious and time-consuming task of manually finding micro-particles of interest among thousands of others on a sample. Running unattended under Windows NT^® FEI's software works completely automatically, on any Phillips' XL-series scanning electron microscope. The software therefore also works with the XL30 ESEM which, because samples do not require conductive coating, is the ideal SEM for forensic investigations.

Most GSR particles have a smaller diameter (between 0.5 and 10 micron). So, large surfaces have to be analyzed to yield results of sufficient statistical validity. This makes manual searching simply impractical. Instead, the GSR package runs unattended analysis on up to 16 samples overnight, leaving the operator to validate and summarize results in the morning. The package can hence give forensic scientists evidence linking suspects with crimes by identifying micro-particles taken from a suspect's skin or clothes.

When a gun is fired, the gunshot residue particles - small particles produced during the gunpowder explosions - are emitted from the back and the muzzle. These particles fly onto the skin and clothing of the person holding the gun. They contain elements that result from the propellant and primer decomposing, as well as from the bullet (which normally contains a large amount of lead), bullet coating or jacket, cartridge components, and previous residues in the barrel. Characteristic elements include antimony (Sb), lead (Pb), barium (Ba) and, for special types of ammunition, titanium (Ti), and Zinc (Zn). These cannot be completely removed by normal washing or cleaning, and samples of the particles can be taken from suspects with adhesive tape for further investigation.

The tape is examiner by a scanning electron microscope (SEM) equipped with an EDX-X-ray microanalysis system, with typically up to 16 samples being analyzed at one time. The position and size of the candidate particles are detected on a backscattered image, and the particles are analyzed with an X-ray detector. The X-ray spectrum emitted from each individual particle is compared against those in the database to verify the particle type. Results are stored on disk in Excel spreadsheet format. An advanced automatic calibration procedure allows complete set-up and dynamic readjustment of the microscope column, motorized stage, backscattered electron detector (BSD) and X-ray analysis system without the need for operator intervention.

The X-ray spectrum emitted by each particle can be classified into one of 35 user definable categories in accordance with the London Metropolitan Police GSR classification scheme. Saving the settings as different configuration files can increase the number of user definable classes. The particles can be reviewed particle by particle, and a single-page easy to read report is automatically generated after each sample has been analyzed. Double clicking on the particle number automatically centers and zooms the particle by the scanning microscope.

Philips' ESEMs have an environmental chamber that images the specimen surface in a gaseous environment at chamber pressures typically in the range of 0.1 to 1.3 mBar or even much higher for out gassing or wet specimens. The ESEM can view objects like plastics, polymers, glass, wood, paints, fibers, hairs, fingerprints, and even insects in their natural uncoated state.

Illustration below: Graphical user interface of the GSR software, showing a typical GSR particle spectrum in combination with the stage configuration set-up and a control area of the Philips XL microscope.